The present invention relates to a casting for housing dynamoelectric machines including an improved ventilation system.
In the construction and operation of dynamoelectric machines, such as a high speed induction motors, the housing or yoke casting often include exhaust vents to permit exit of the hot air from the inside of the machine. Often such "open" machines are intended for use in environments where they are exposed to precipitation including rain and snow, as well as airborne particles which present a hazard to machine parts. To minimize the entrance of precipitation and foreign objects and particles including operators' fingers, external devices such as louvers, grills, screens, and other similar attachments have been affixed to the housing to shield the openings. Also, various flow designs have been devised to allow ventilation of the interior of the machine, while protecting the machine from precipitation.
For example, the patentees of U.S. Pat. No. 4,766,337 state that ventilation in a dynamoelectric machine can be improved by providing an air inlet ring overlapping the gap between the frame member and the bearing bracket. The patentees state that incoming cooling air moves axially along the air inlet ring, past an air deflector and exits from the machine at a port located intermediate the ends of the frame member.
According to U.S. Pat. No. 3,610,976, a drip-proof electric motor can have a casing with air vents spaced near both ends and in the end walls.
The foregoing attempts to provide adequate ventilation for motors intended for outdoor use or other adverse environments often do not provide enough ventilation for high speed induction motors, for example.